The dashed curves in Fig. REF  show the dependence of \(A_{\rm eff,D}\)  on
the lightest neutrino mass for complete helicity flip,
\(\theta _i = \pi \) . For partial spin rotation, \(A_{\rm eff,D}\)  lies
between the solid and dashed curves.
When \(\theta _i=\pi /2\) , the amplitudes to be left handed and right handed are equal and \(A_{\rm eff,D}=1\) .
To illustrate the qualitative dependence of the
helicity-flip probability on the neutrino magnetic moment in Fig. REF , we show \(A_{\rm eff,D}\)  for
Dirac neutrinos passing through the Milky Way as the dash-dot curve, calculated from Eq. (REF ) for small angle bending with the characteristic
parameters \(B_g = 10\,\mu \) G and \(\Lambda _g\) = 1 kpc, and
with  \(\mu _\nu = 5\times 10^{-14} \mu _B\) , a factor of 5 larger than the naturalness upper bound [1]}, but two orders of magnitude smaller than the magnetic moment XENON1T would need to explain their excess of low energy electron events. If the magnetic moment of normal hierarchy Dirac neutrinos is of order that suggested
by XENON1T, then for the characteristic parameters assumed for cosmic
or galactic magnetic fields the rotation of the neutrino spins would no
longer be small, with the consequence that the mean \(\cos \theta \)  are small,
and \(A_{\rm eff,D}\)  would be decreased to essentially unity, with a
concomitant decrease in the ITBD detection rate.  A magnetic moment
of the standard model prediction of Eq. (REF ) would affect \(A_{\rm eff,D}\) 
insignificantly.
